Plug, and methods for setting and releasing the plug

ABSTRACT

A plug includes a slip actuator for setting and release of slips, and a locking element in contact with the slip actuator. The locking element includes multiple parts with internal threads which constitute an enclosure around threads of a pipe. On the radial outer surface of the locking element are provided resilient elements. When setting the plug, the locking element is capable of sliding over the pipe threads for movement of the slip actuator and setting of the slips, until the locking element comes into engagement with a locking sleeve, fixed relative to the pipe, which prevents rotation of the locking element. When releasing the plug, the locking element is released from the locking sleeve, and the locking element rotates off the pipe threads, and the slip actuator follows the movement of the locking element and releases the slips.

INTRODUCTION

The present invention relates to a plug and to methods for setting andreleasing the plug in a well, for example, a hydrocarbon well, asdisclosed in the independent apparatus claim and in the independentmethod claims.

BACKGROUND/PRIOR ART

It is common practice to close off the borehole, either temporarily orpermanently, by using plugs. The background for this may be that it isdesirable, for example, to carry out tests or maintenance in the well.The plugs are usually run down the well using a running tool. When theplug has reached the desired depth in the well, it is secured to thesurrounding casing or borehole wall using anchoring elements. Theborehole is subsequently sealed, often by using packers which seal thearea between the pipe or plug and the borehole wall. The bridge plugshown in U.S. Pat. No. 6,220,348 B1, and the whole running tool, must bepulled out of the well if another operation is to be carried out in thewell, which will mean a great deal of extra time and costs.

Known plugs for use in wells have the disadvantage that the plugsrequire maintenance between each operation.

It is usual to set and release plugs by means of rotation, but it can bedifficult to achieve controlled rotation at great well depths. There areseveral potential sources of error which make the setting and releasehazardous. One such source of error could be left-hand (anti-clockwise)rotation, which may result in equipment such as drill pipes or plugsbeing unscrewed from one another.

It is an object of the invention to resolve some of the drawbacks of theprior art. The object is achieved by means of a plug and methods for itssetting and release according to the independent claims, withembodiments of the invention disclosed in the dependent claims. Thesetting and release take place essentially by means of axial movement ofthe pipe. By this is meant that an up-and-down movement applied to theplug is transmitted into a rotational movement that applies to the pluga moment which it wishes to release through a locking system. Anotherobject is to provide a plug which can be used for several operations ina well with little call for maintenance of the plug between thedifferent operations.

In the present invention, according to independent claim 1, a plug for ahydrocarbon well is defined, wherein the plug can be held in placerelative to a casing/borehole, and wherein the plug further comprises aslip actuator for setting and releasing slips, a locking element incontact with the slip actuator, and one or more resilient packingelements which are adapted for sealing against the casing/borehole wall,and wherein the locking element comprises multiple parts having internalthreads which constitute an enclosure around threads on a pipe, andwhere on the radial outer surface of the locking element there arearranged resilient elements, and that

-   -   the locking element, when setting the plug, is capable of        sliding over the pipe threads for movement of the slip actuator        and setting of the slips, and that the locking element comes        into engagement with a locking sleeve to prevent rotation of the        locking element,    -   whilst when releasing the plug, the locking sleeve is released        from the locking element, the locking element rotates off the        pipe threads and the slips are released.

The invention also relates to a method for setting the plug in a well,wherein the setting is activated by an axial movement of the pipe, andwhere the movement further causes a guide sleeve to apply a force on thelocking element which, by means of its high-pitch threads against thepipe, will slide over the threads and exert a force on the slip actuatorwhich presses the slips out into firm engagement with thecasing/borehole wall. By high-pitch threads here is meant threads thatwill rotate off a corresponding threaded part in only a few turns.

The invention relates also to a method for releasing the plug wherein anaxial movement of the pipe activates the release of the locking sleevefrom the locking element, such that the locking element is free torotate off the threads on the pipe and the slips are released. Axialmovement may be a movement up or down, or a combination thereof.

The setting or release of the plug should not take place unless desired.Up and down movement of the vessel, as a consequence of the rolling ofthe sea, may inadvertently start the setting. To avoid undesired settingand release, a first and a second hydraulic timer may be provided inconnection with the plug for setting and release, respectively. Thetimers, one for setting and one for release, ensure that the setting orrelease does not start until the pressure from the surface acts over agiven time period. The timers each consist of two hydraulic fluidchambers, where fluid from one of the chambers starts to flow over intothe other chamber as a result of pressure that is applied to the pipefrom the surface. If the pressure is not applied for a sufficiently longtime, as, for example, on the heave of the waves, all the fluid will notflow between the chambers, and the setting or the release will not bestarted. Once all the fluid has flowed between the chambers, the settingor the release will start.

On the pipe there may be provided at least one fixed pin that is movablein a recess in a guide sleeve on the plug. The recess in the guidesleeve may be helical. This makes it possible for the operator to knowat all times where the plug is in the setting or release process, inthat the pin element follows the axial movements of the pipe,up-down-up, as the pipe is pushed down into the well or pulled upwards.An axial movement of the pipe, and thus of the pin in the recess, willcause the axial movement to be transmitted into a rotational movement ofthe guide sleeve depending on the form of the recess.

A holding member with radially acting elements can hold the plugessentially fixed to the casing/borehole wall during the setting. Duringthe setting, but not necessarily during the release, the holding memberwill be in end contact with a guide sleeve, and a locking element willbe in end contact with the second end of the guide sleeve.

In an embodiment, the setting involves that a locking element withlocking grooves, which during setting of the plug is so arranged as toallow the locking element on an axial movement of the pipe to slide overcorresponding threads on the pipe, engages with corresponding lockingpins on the locking sleeve and is prevented from being screwed off thethreads. The locking sleeve is held fixed in the rotational direction,but is movable in an axial direction relative to the pipe. Theconfiguration of the locking grooves on the locking element and thelocking pins on the locking sleeve may be any configuration suitable toprevent rotation. On locking, and before the locking element is lockedin the locking sleeve, the axial movement of the pipe will set slips,and the plug will be anchored to the casing/borehole wall. Resilientpacking elements arranged on the plug seal against the casing/boreholewall when compressed. In connection with the compressible resilientpacking elements, one or more backstop elements are provided which arefixed relative to the pipe. The backstop elements follow the movement ofthe pipe, and a further movement of the pipe, after the slips have beenset, will cause the resilient packing elements to be compressed betweenthe slips and the backstop elements.

When releasing the plug, the pipe is by means of the running tool rundown to the plug. A timer controls the activation of the release. Afterthe activation of the timer, the pipe is moved a given length. Thismovement causes the slips to be released thereby releasing the anchoringagainst the casing/borehole wall, and the engagement between the lockinggrooves on the locking element and the locking pins on the lockingsleeve is broken. On release of the slips, the holding force from theslips against the resilient packing elements is removed. The resilientpacking elements will therefore no longer be kept compressed, but arefree to expand in an axial direction. The axial force from the resilientpacking elements will act on the locking element such that the lockingelement rotates off the threads on the pipe.

DESCRIPTION OF THE INVENTION

One embodiment of the invention will now be described with reference tothe attached drawings, wherein:

FIG. 1 shows a plug coupled to a running tool and a pipe at the start ofsetting;

FIG. 2 shows the setting according to FIG. 1 with the slips out;

FIG. 3 shows the beginning of the release of the plug;

FIG. 4 shows the release of the plug;

FIG. 5 shows a locking element on the outer surface of a pipe, and alocking sleeve;

FIG. 6A shows a pin arranged on a pipe, where the pin is in a firstposition, movable in a recess on a guide sleeve;

FIG. 6B shows the pin in a second position, where the pipe is pulledtowards the surface;

FIG. 6C shows the position of the pin in the recess as the settingprocess starts and the pipe is pushed downwards;

FIG. 6D shows the pin in its end position when the setting process hasbeen completed;

FIG. 7 shows the timer function of the present invention.

DETAILED DESCRIPTION

Reference is first made to FIGS. 1-4, which show a plug 1 coupled to arunning tool 13 and a pipe 15. The lower end of the plug is shown to theright in the figure. The internal pipe of the plug 1, the running tool13 and the pipe 15 are referred to below as pipe 15. At the lower end ofthe plug 1 there is arranged a holding member 10 with radially actingelements 12 for holding the plug fixed relative to the casing/boreholewall, see FIG. 2. There is further shown a first 2 and a second 42hydraulic timer which control the activation of the setting and therelease of the plug 1. Furthermore, a pin 3 is arranged on the lower endof the pipe 15. A guide sleeve 4, which is a part of the plug 1, has arecess 16 in which the pin 3 can move. Arranged in end contact with theguide sleeve 4 is a rotatable locking element 5, consisting of multipleparts, having internal high-pitch threads 17 capable of engaging withcorresponding high-pitch threads 18 on the radial outer surface of thepipe 15, best shown in FIG. 5. Furthermore, on the radial outer surfaceof the locking element 5 there are resilient elements 6 which form anenclosure around the parts that constitute the locking element 5.

The locking element 5 has arranged at one of its end portions lockinggrooves 11 capable of engaging with corresponding locking pins 19 in alocking sleeve 7. The locking sleeve 7 is fixed in the rotationaldirection but is movable in an axial direction, see FIG. 5. The lockinggrooves 11 on the locking element 5 are formed of radially inward facingpins. The corresponding locking pins 19 on the locking sleeve 7 consistof axially projecting pins, which are locked in the locking grooves 11on the locking element 5. On the radial outer surface of the lockingsleeve 7 is a slip actuator 8, which is capable of coming into contactwith the locking element 5, see FIGS. 1 and 2. The slip actuator 8 hasat least one conical end portion which is adapted for pushing slips 9out into engagement with the casing/borehole wall in order to secure theplug 1 in the well.

At the upper end of the plug 1, resilient packers 20 are provided whichseal between the pipe 15 or plug 1 and the casing/borehole wall. Inconnection with the resilient packing elements 20, backstop elements 41are arranged thereabove that are fixed relative to the pipe 15 andfollow the movement of the pipe 15.

Setting

FIGS. 6A-6D show, step by step, the position of the pin 3 in the recess16 during the process of setting the plug 1.

During the running down of the pipe 15, the pin 3 is in the positionshown in FIG. 6A. When the plug is at the desired depth in the well, therunning down of the pipe 15 with the attached running tool 13 and theplug 1 is stopped, and the setting process starts. The pipe 15 is pulledback slightly, and the pin 3 follows the recess 16 to its next positionin the guide sleeve 4 (FIG. 6B), which causes the guide sleeve 15 torotate as a result of the movement of the pin 3 in the recess 16.Pressure is then applied from the surface over a predetermined period oftime whilst the pipe 15 is run down. The pin 3 will then follow the pipe15 and come into the position shown in FIG. 6C, where the settingprocess starts. The pipe 15 is subsequently pushed on downwards untilthe pin 3 reaches the vertical end position in the recess 16 (FIG. 6D).

The time interval for how long pressure is to be applied to the pipe 15is determined in advance, and is given by how long it takes before allfluid in the hydraulic timer 2 has migrated from the first chamber tothe second chamber, see FIG. 7. Such a time period is, for example, setto at least 20 seconds so as to prevent the axial movement of the pipe15 from being confused with natural heave motions of the vessel owing tothe motion of the sea. The first 2 and the second 42 hydraulic timer maytherefore be regarded as a dampener for the setting and release,respectively, as it filters out the natural heave motions of theplatform, and only activates the setting and release of the plug whenthe pressure on the pipe 15 has acted for at least as long as thepredetermined time period.

When all fluid has flowed over from one chamber to the other chamber inthe first hydraulic timer 2, the setting of the plug 1 starts. A holdingmember 10 with radially acting elements 12 on the plug 1 essentiallyholds the plug 1 fixed to the casing/borehole wall, see FIGS. 1-4. Thepipe 15 is moved down and the pin 3 follows the vertical groove in FIGS.6C and 6D in the recess 16 on the guide sleeve 4, whilst the radiallyacting elements 12 on the holding member 10 hold the plug 1 fixedrelative to the casing/borehole wall. The guide sleeve 4, wherein thepin 3 follows the recess 16, is in abutment with the holding member 10secured to the casing/borehole wall, and will exert a force against thefirst end of the above-lying locking element 5, see FIG. 2. The lockingelement 5, which consists of multiple parts with internal high-pitchthreads 17, has resilient elements 6 on its outer surface which enablethe locking element 5 to slide over the corresponding high-pitch threads18 on the pipe 15, see FIG. 5. The resilient elements 6 on the outersurface of the locking element 5 have as their only purpose to holdtogether the multiple parts which constitute the locking element 5, anddo not represent any major force on the locking element 5 in the radialdirection against the pipe 15. This means that the internal threads 17of the locking element, during the setting of the plug 1, slide over thethreads 18 of the pipe 15, without being screwed on. The locking element5, at its other end, is in abutment with a slip actuator 8 which restsagainst the radial outer surface of the locking sleeve 7. An upwardlydirected movement of the locking element 5 will exert an upward movementon one end of the slip actuator 8. The slip actuator 8 may be conical atits other end and an upward axial movement of the slip actuator 8 willpress the slips 9 out into engagement with the casing/borehole wall, seeFIG. 2. At the same time, as can best be seen from FIG. 5, when theinternal threads 17 of the locking element 5 essentially completelycover the pipe threads 18, locking grooves 11 on the locking element 5will engage with corresponding locking pins 19 on the locking sleeve 7and ensure that the locking element 5 is held locked in the rotationaldirection. The locking sleeve 7 is secured to the pipe 15 in therotational direction and rotational forces from the locking element 5will be locked in the locking sleeve 7. The locking element 5 is nowsecured to the locking sleeve 7, the slips 9 are in contact with thecasing/borehole wall, and the plug 1 is secured in the well. The pin 3in the recess 16 is now in the vertical end position, as shown in FIG.6D. After the slips 9 have been set and the pin 3 has reached itsvertical end position, pressure is again applied from the surface on thepipe 15 such that the resilient packing elements 20 are compressedbetween the secured slips 9 from below and the backstop elements 41 fromabove. In this way, the wellbore is sealed between the pipe 15 or theplug 1 and the casing/borehole wall by the resilient packing elements20. The pipe 15 with the attached running tool 13 can be released fromthe plug 1, and the plug 1 can be left in the well.

Release

When the plug is to be released from the casing/borehole wall, the pipe15 is run down into engagement with the plug by the associated runningtool 13, see FIG. 3. Pressure is then applied from the surface over agiven period of time such that the second hydraulic timer 42 activatesthe release. When the running tool 13 is fastened to the plug 1, and thesecond hydraulic timer 42 has activated the release, the pipe 15 ispulled up. The corresponding locking grooves 11 and the locking pins 19between the locking element 5 and the locking sleeve 7 will be separatedfrom each other. The locking element 5 will now no longer exert anyupward force on the slip actuator 8. The slips 9 will therefore bereleased from the casing/borehole wall. When the slips 9 are no longerset, the resilient packing elements 20 will no longer be subjected toany force from below from the slips 9, but only from above by thebackstop elements 41. The resilient packing elements 20 will thereforeexpand and act as a spring against the locking element 5 and press onthe locking element 5 in an axial direction such that the lockingelement 5 rotates off the threads 18 on the pipe 15. The radially actingelements 12 on the holding element 10 will furthermore be released fromthe casing/borehole wall and the plug 1 is free to be removed from thewell, see FIG. 4.

The invention has now been explained with reference to one embodiment. Aperson of skill in the art will understand that changes andmodifications may be made to the embodiment described which are withinthe scope of the invention as defined in the attached claims.

1. A plug for a hydrocarbon well, wherein the plug can be held fixedrelative to a casing/borehole wall, and wherein the plug furthercomprises: a slip actuator for setting and releasing slips, a lockingelement in contact with the slip actuator, and one or more resilientpacking elements which are adapted for sealing against thecasing/borehole wall, wherein the locking element comprises multipleparts having internal threads which constitute an enclosure aroundthreads on a pipe, and wherein on the radial outer surface of thelocking element there are arranged resilient elements (6), and whereinthe locking element, when setting the plug, is capable of sliding overthe pipe threads for movement of the slip actuator and setting of theslips, and that the locking element comes into engagement with a lockingsleeve in order to prevent rotation of the locking element; whilst whenreleasing the plug, the locking sleeve is released from the lockingelement, the locking element rotates off the pipe threads and the slipsare released.
 2. The plug according to claim 1, wherein the plug is heldfixed to the casing/borehole wall by a holding member with radiallyacting elements.
 3. The plug according to claim 1, wherein the settingand the release of the plug is controlled by axial movement of the pipe.4. The plug according to one of claim 1, wherein the holding member isin end contact with a guide sleeve and that the locking element is inend contact with the other end of the guide sleeve.
 5. The plugaccording to claim 1, wherein a pin is provided on the pipe whichfollows the movement of the pipe, the pin being movable in a recess inthe guide sleeve.
 6. The plug according to claim 1, wherein the lockingelement and the locking sleeve have corresponding locking grooves andlocking pins.
 7. The plug according to claim 1, wherein the activationof the setting of the plug is controlled by a first timer that isactivated by a specific pressure on the pipe over a given period oftime.
 8. The plug according to claim 7, wherein the at least one timeris hydraulic, and that the pressure acting on the timer controls thetransfer of hydraulic fluid from a first chamber to a second chamber inthe timer, and where the setting starts when all hydraulic fluid hasbeen transferred between the chambers.
 9. The plug according to claim 1,wherein the activation of the release of the plug is controlled by asecond timer which is activated by a specific pressure on the pipe overa given period of time.
 10. The plug according to claim 7, wherein theat least one timer is hydraulic, and that the pressure that acts on thetimer controls the transfer of hydraulic fluid from a first chamber to asecond chamber in the timer, and where the release starts when allhydraulic fluid has been transferred between the chambers.
 11. The plugaccording to claim 1, wherein the resilient packing elements arecompressed by setting of the slips, and on the release the resilientpacking elements expand axially, this axial expansion motion rotatingthe locking element off the pipe threads.
 12. A method for setting theplug according to claim 1, wherein the setting is activated by an axialmovement of the pipe, wherein the movement further causes a guide sleeveto apply a force on the locking element which, by virtue of itshigh-pitch threads against the pipe, will slide over the threads andexert a force on the slip actuator which presses the slips out into firmengagement with the casing/borehole wall.
 13. A method for release ofthe plug according to claim 1, wherein an axial movement of the pipeactivates the release of the locking sleeve from the locking element,such that the locking element is free to rotate off the threads on thepipe and the slips are released.
 14. A method according to claim 13,wherein the locking element rotates off the threads on the pipe in thatresilient packing elements on the plug expand axially and act on thelocking element.